This invention relates to an arrangement for obtaining flux rate of change information in a magnetic circuit such as may be used for vibration attenuation in a magnetic forcer system.
Passive arrangements for the purpose described include spring/mass systems, mechanical dampers and hybrid visco-elastic devices. Active arrangements may be open or closed loop and may include forcer elements or drive elements such as piezoceramic elements, pneumatic/hydraulic drives, or electromagnetic devices which, when used in conjunction with appropriate sensing elements, can be used to actively accomplish the aforenoted vibration attenuation.
In an active open loop configuration, a command matching the vibration to be attenuated as a function of time is applied to the forcer element. This configuration works well when the vibration dynamics can be modeled accurately. Alternatively, an active closed loop arrangement can be employed, whereby the vibration is sensed and the sensed information is used to adjust a command matching the vibration.
The present invention is similar to the above described active closed loop arrangement which uses "Hall Effect" devices to measure magnetic flux within an air gap. These devices are operative so that presence of a magnetic field of a proper orientation induces a small voltage in a semiconductor device. The Hall Effect arrangement uses flux as the sensed parameter for vibration attenuation. The present invention, on the other hand, uses flux rate for this purpose.
Accordingly, it is the object of the present invention to use a closed loop or feedback arrangement for sensing flux rate of change in a magnetic circuit. In this regard, it is noted that in the present invention the closed loop is tuned whereby a narrow range of vibration frequencies are attenuated as may be desired. This is in contrast to the invention disclosed and claimed in the aforenoted U.S. Pat. No. 5,329,416 wherein the closed loop is broadband in that a broad range of vibration frequencies are attenuated as likewise may be desired.